The present invention relates to a thermal head for use in recording data, and more particularly, to a driving IC circuit mounted thereon.
As data recording apparatus various types of thermal heads are known and widely used, among which is a type in which a heating resistor group, a transistor array and a shift register are provided. The heating resistor group consists of 2n pieces of heating elements, which are adjacently paired for making connections to two common electrodes alternately. The transistor array consists of n pieces of transistors, against which the heating elements are also adjacently paired for being connected to the individual transistors. Each transistor is connected to the shift register so as to receive signals therefrom. In this arrangement, when the heating elements are to be selectively driven, a voltage is applied to either of the two common electrodes, thereby energizing one group of the heating elements connected thereto. Then, a voltage is applied to the other common electrode, thereby energizing the remaining heating elements. At each time signals must be transferred to the shift register, because the transistor array only act as buffers for switching the heating elements. As evident from the foregoing description, this known type of thermal head has a disadvantage that the printing data must be transferred to the shift register one portion after another. Another disadvantage is that it is impossible to transfer printing data in the positional order of the heating elements. This type will be explained in detail below.
Another prior art thermal head is disclosed in U.S. Pat. No. 3,984,844, which is characterized by a plurality of electrodes arranged alternately on both sides of a strip-like region of an insulated substrate, with a plurality of heating resistor elements bridging the electrodes. In this arrangement a voltage is selectively applied to the electrodes on one side of the strip-like region and those adjacent thereto on the other side of the region, thereby energizing the heating resistor elements. In this way a visual recording of data is effected due to the heat generated by the particular heating resistor elements. However, the shift register provided in the driving circuit is only for storing n-bit signals corresponding to the 2n pieces of heating resistor elements. As pointed out with respect to the first-mentioned prior art thermal head, the printing data must be transferred to the shift register one portion after another, and it is also impossible to transfer the printing data in the positional order of the heating resistor elements. If it is to be achieved, the circuit will become extremely complicated.